> selects all direct descendants/children
A space > selector will only select all immediate descendants. See fiddle for example.
div { border: 1px solid black; margin-bottom: 10px; }
.a b { color: red; } /* every John is red */
.b > b { color: blue; } /* Only John 3 and John 4 are blue */
John 1
John 2
John 3
John 4
John 1
John 2
John 3
John 4
